import math

x1,y1,x2,y2=map(float,input().split())
answer=(math.sqrt((x2-x1)**2+(y2-y1)**2))
print("{0:.8f}".format(answer)) import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 answer=(math.sqrt((x2-x1)**2+(y2-y1)**2)) answer math.sqrt((x2-x1)**2+(y2-y1)**2) math.sqrt math sqrt (x2-x1)**2+(y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 print("{0:.8f}".format(answer)) print "{0:.8f}".format(answer) "{0:.8f}".format "{0:.8f}" format answer y2=map(float,input().split()) map(float,input().split()) y2 x2,y2=map(float,input().split()) map(float,input().split()) x2 y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 answer=(math.sqrt((x2-x1)**2+(y2-y1)**2)) math.sqrt((x2-x1)**2+(y2-y1)**2) answer
import math

x1,y1,x2,y2=map(float,input().split())
answer=(math.sqrt((x2-x1)**2+(y2-y1)**2))
print("{0:.8f}".format(answer))